Inertial navigation systems (INS) are used to determine parameters such as position, orientation, and velocity in a moving platform such as an aircraft, a spacecraft, a watercraft or a guided missile. The INS calculates these parameters using dead reckoning without the need for external references.
At the heart of the INS is an inertial measurement unit (IMU). The IMU typically includes three motion sensors (accelerometers) and three rotation sensors (gyroscopes). The three motion sensors are placed such that their measuring axes are orthogonal to each other. Similarly, the rotation sensors are also placed in a mutually orthogonal relationship to each other. The IMU provides measurements of motion and rotation to the INS to derive a navigation solution composed of position, orientation and velocity.
One known problem with an INS is error accumulation. Each measurement made by the IMU has an inherent error. Over time, the INS adds current measurements from the IMU to prior navigation solutions. Thus, with the addition of each measurement, the INS accumulates additional errors in the produced navigation solution.
The accuracy of the INS is improved by using outputs of additional sensors that effectively bound the error of the INS. For example, INS systems typically include one or more of global positioning system (GPS), Doppler, and other sensors that provide inputs to the INS to offset the accumulated errors.
In a recent development, personal navigation systems are being developed based on an INS platform. Such personal navigation systems can be used by emergency responders so that the position and movement of each responder in a three-dimensional structure can be instantaneously displayed in a command center. However, several problems are inherent in the design of personal navigation systems. First, an INS platform typically has a high power requirement due to the IMU and the other sensors required for accurate position, velocity and orientation information. Further, the size of a typical INS may be larger than desirable for personal navigation systems.